Thermal relay unit



March 14, 194 P. M. CHRISTENSEN ,3

THERMAL RELAY UNIT Filed Jan. 4, 1941 Z m F- 5 /0 wry/10000017004111 170 MISULATION PEMZM 57:12:52: 275527 .5 J. W. J mist :02??

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Patented Mar. 14, 1944 THERMAL RELAY UNIT Paul M. Christensen,Newington, Conn., assignor to Colts Patent Fire Arms ManufacturingCompany, Hartford, Conn., a corporation of Connecticut ApplicationJanuary 4, 1941, Serial No. 373,189

20 Claims. (01. zoo- 122) The invention relates to thermal relays, andthe general object of the invention is to provide a thermal relay forelectromagnetic motor starters, and including a quick acting switchactuated by deflection of a thermostatic element to interrupt a circuitunder abnormal current conditions; and means to make the relay eitherautomatically or manually resettable to re-establish the interruptedcircuit when normal current conditions again prevail in the circuitcontrolled by the motor starter; the construction and arrangement beingsuch as to provide a complete and compact thermal relay embodying theabove features conveniently connectible electrically and mechanicallywith the motor starter and its support to provide a unitary structure.

An important feature of the invention is the provision of means formaking the relay operable either automatically or manually to reset it,that is, to, re-establish an electric circuit which has been interruptedby the relay because of abnormal conditions in the circuit. Theinvention accomplishes this by a simple and easily operated constructionand arrangement of parts on the relay casing and accessible formanipulation without in any way altering the electrical connections ordisturbing the original arrangement of the parts of the relay in theirassembled relation. More specifically this is accomplished by theprovision of a device, simple in construction and easily assembled onthe housing, which is positionable either in operative relation withrespect to the movable electric contact arm of the relay, or ininoperative position in the relay casing with respect to the movablecontact arm, in which positions, respectively, the relay is manually andautomatically resettable as hereinafter explained in detail.

Another. important feature of the invention resides in the provision ofa relatively light but extremely quick acting switch, the parts of whichmay be manufactured and assembled in operative relation with respect totheir operating and operated mechanism cheaply and with facility.

Still another feature of the invention resides in the construction ofthe body or casing of the relay itself in regard to its adaptability asa unitary part of an electric motor starter, as well as from thestructural standpoint. With regard to the latter, the details of theconstruction and arrangement of the casing and the manner of- In theaccompanying drawing I have shown thenow preferred embodiment of theinvention, but it will be understood that the drawing is intended forillustrative purposes only and is not to be.

construed as defining or limiting the scope of the invention, the claimsforming a part of this specification being relied upon for that purpose.

In the drawing:

Fig. 1 is a front elevational view of an electromagnetic motor startershowing two thermal relays embodying the present invention mounted onthe base supporting the motor starter, the casing cover being brokenaway; and one of the thermal relays being shown in section taken on theline l--l of Fig. 2;

Fig. 2 is a sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a sectionalview taken on the line 3-3 of Fig. 1;

Fig. 4 isv a sectional view taken on the line 4--4 of Fig. '7; showingthe switch in open circuit position, and the relay operable asautomatically resettable.

Fig. 5 is a sectional view similar to Fig. 4, showing the switch inclosed circuit position, and the relay operable as manually resettable;

Fig. 6 is a'sectional view similar to Fig. 5 showing the switch in opencircuit position and held against closing the circuit by the manuallyoperable reset means;

Fig. '7 is a view taken on the line 11 of Fig. 1 and showing the relayas being arranged to'operate as automatically resettable;

Fig. 8 is a sectional view taken on the line 8-8 of Fig. 5;

Fig. 9 is a sectional view similar to Fig. 8 showing the parts in theirrelative positions of Fig. 6; and

Fig. 10 is a detail view showing the switch operating link in plan andthe switch lever in section on an enlarged scale.

Referring to the drawing and particularly to Figs. 1 and 2 thereof, thenumeral l0 designates a casing in which a unitary electro-magnetic motorstarter and thermal relays embodying the present invention is housed.The electro-magnetic motor starter and thermal relays are mounted on abase II, and the base is secured to the bottom of the casing III bysuitable means such as screws i2, only one of which is shown in thedrawing. The motor starter includes a stationary insulating contact baseit which is shown fastened to the base II by screws l4 which extendtherethrough and engage in screw threaded openings in the base II.

A frame II is statlonarily mounted on the base H by suitable means, notshown, in spaced relation to the stationary insulating contact base (I,and houses the electro-magnet of the motor starter. The coil ll of theelectro-magnet is shown held against accidental movement in its housingI! by a removable yoke member H, which is not shown nor described indetail in this application since it is not a part of the presentinvention. The electro-magnet is adapted to reciprocate an armature It.To afford easy guided movement to the armature, it is suitably attachedto a carrier frame H, which is not shown nor described in detail in thisapplication, but which is slidably supported in the frame IS. A movableinsulating contact carrier is attached to the movable frame I! forreciprocating movement in the space between the stationary contact baseI! and the fixed frame or electro-magnet housing II to bring contacts 2|into bridging relation with respect to contacts 22 on the stationaryinsulating base II, when the armature J! is attracted by theelectro-magnet and causes frame I! and carrier 28 to move. Obviouslywhen the armature is released it drops and causes carrier 20 andcontacts 2| to move away from contacts 22.

A push button control station 23 is convenlently mounted on the top 01'the electro-magnet housing I5 with the "start" and "stop push buttonsexposed through the cover of the casing for manual operation; andsuitable connection bindin! P sts 24 are provided for making desiredcircuit connections.

Figs. 1 and 2 of the drawing show two thermal relays, designatedgenerally by the numeral 25, and embodying the present invention,mounted on the base II at opposite sides of the frame It. The relays areidentical in construction but reversed as to position. Only one of therelays will be described, the reason for showing two relays being toillustrate a complete actual magnetic motor starter unit adapted tocontrol different circuits. Each relay body or casing is shown ascomprising a relatively thick part or block 28 of molded insulatingmaterial, and a. plate 21 of molded insulating material. The parts 26and 21 of the casing are separableaipon removal of a screw, not shown,which extends through the plate 21 and engages in a screw threadedopening 28 (Fig. 7) in the block. The opening 28 is located at thebottom of a recess 29 which receives a correspondingly shaped projectionon the plate 21 and through which the screw extends. Each casing 25,with the mechanism of the thermal relay switch assembled thereon ispositioned on the base II with the plate 21 against frame l5 of themagnetic motor starter and with openings 30 in alignment with screwthreaded openings in the sides of theframe l8. Screws 3| are theninserted through the openings 30 and threaded into the openings in theframe I5 to hold the relays in their established places as part of theunitary structure of the magnetic motor starter.

The relay casing part 26 is substantially rectangular in form, and hasan outwardly extending projection I3 on its top. Two of the top cornersone at each side of the projection 31, are cut away to provide shoulders34 for reception of stationary electrical terminal members or contactplates 35 and 38 which receive the terminal binding posts 35' and 34' toelectrically connect the relay switch, hereinafter described, to theelectro-magnet of the motor starter. The arm of the contact plate 35which receives the binding post 35 overlies one of the shoulders 34, andthe other arm of the contact plate is flatly disposed against the faceof the casing part 28 at one end thereof. The plate 38 is similarlymounted on the other shoulder 34, and will be hereinafter described morein detail in connection with the switch mechanism. When the plate 21 isattached to the part 28 the structure of the casing then providesrecesses at the cut away corv ners and shoulders 34 in which the bindingposts 35', 36' are located (Fig. 1). The relay casing part 26 is open atits front, and a removable closure plate 31 forms, in conjunction with atransverse partition plate 38 and walls of the casing, a chamber toreceive and house an electric resistance unit and a bimetallicthermostatic element.

The construction of the electric resistance unit does not form part ofthe present invention, and the description of the one illustrated willbe general, since various types of electric resistance units can beemployed. In the drawing (Figs. 2 and 8), the resistance unit comprisesa plate 39 of insulating material supporting a grid 40, the terminals ofwhich are looped around eyelets 4| on the insulating plate 39. The plate3!! partially overlies and thus covers a portion of a notch in the topof the casing part 26 through which the grid is insertible into andremovable from the casing 25. The eyelets 4| engage or rest on the topsof stationary electric contact plates 42 which are secured to the top ofthe casing by any suitable means. Screws or terminals 43 engage threadedopenings in the contact plates 42 and the heads of the screws engage thetops of the eyelets 4| through which the screws extend to detachablymount the electric resistance unit in operating position-in the relaycasing. Binding posts 44 on the stationary contact plates 42 areprovided for electrically connecting the resistance unit in electriccircuits which the thermal relay and motor starter are to control.

The thermostatic element which operates the switch hereinafterdescribed, comprises a bimetallic plate 45, one end of which is rigidlysecured to a bracket 46 in any suitable manner. The bracket 46 issubstantially Ushaped, and a screw 41 is threaded through openings inthe arms of the bracket for calibrating purposes in properly locatingthe bimetallic plate 45 relative to the grid 40 in its operative Psition in casing 25. The bracket has an extension 48 (Fig. 2) whichreceives screws 49 extending through the casing part 26 to firmly butdetachably secure the bracket to the casing and maintain the bimetallicplate, in its normal condition, in properly adjusted relation withrespect to the grid 40, so that the bimetallic plate will be deflectedto operate the switch, about to be described, to interrupt the circuitwhen abnormal conditions therein cause the resistance unit to beoverheated.

Although the grid 40 is shown in the drawing as being positioned infront of the bimetallic plate 45 in the said casing chamber, thisarrangement can be reversed, that is, the bimetalaasaaea lic plate canbe positioned in front of the grid because the grid is removable fromthe top oi the casing independently of the bimetallic plate. Of course,under such reversed arrangement the bimetallic plate would be secured toits supporting bracket with its other face confronting the grid toobtain deflection of the plate in the same direction as illustrated inthe drawing to properly operate the switch without changing or alteringthe structure presently described.

The bimetallic plate 45 has a tongue 56 on its free end, and the tongueextends through a slot in the reduced portion 52 of a slide or link inthe nature of a strip of insulating material,

' to detachably connect the bimetallic plate and slide. Obviously,movement of the bimetallic plate during deflections under thermalconditions to which it is subjected in the relay casing will impartmovements to the slide or link. The casing part 26 is provided withchannels 58 (Fig. 7) which receive the longitudinal edges of theenlarged portion 54 of the slide or link to support it and guide itduring its movements. The reduced portion 52 of the slide or linkextends through a slot 55 (Fig. 2) in the partition plate 38 in casingpart 26, and this arrangement also assists in supporting and guiding theslide or link.

It will be noted, (Figs. 4-9) that a chamber 56 is provided in the rearof casing 25 longitudinally thereacross being formed by walls of thepart 26, the partition plate 38, and the casing plate 21, to house theswitch mechanism; and the enlarged portion 54 of the slide is locatedtransversely across the chamber 56 to actuate the lever 51 of the quickaction switch. The switch lever 51 is preferably formed from a thinstrip of metal the central area of which is struck-up to impart rigidityto the strip, the struck-up area or hump being designated by the numeral58. The provision of the struck-up area 58also stabilizes the leverduring its working movements. The area 58 is located, as shown best inFig. 10, through a slot 59 in the portion 54 of the slide, and the slot58 has a straight side and a convex side. The hump or struck-up area 58engages the convex side of the slot while the straight portions of thelever 51 at the sides and base of the struck-up portion 58 engage thestraight side of the slot, thus providing a threepoint mechanicalcontact between the slide and lever 51, which rocks relative to theslide during actuation thereof. The lever 51 has a tongue 60 extendingfrom one of its ends into an opening in the bottom of the trough of asubstantially V-shaped saddle 6|, which is seated in a recess providedtherefor in the wall of the casing part 26 at one end of the chamber,56, serving to fulcrum said end of the lever. The other end of the lever51 is notched for reception of one end of a substantially U-shapedover-center spring 64, the other end of which is similarly arranged inthe notched end of a movable electrical contact arm 65 to mechanicallyconnect the switch and movable electric contact arm for operation in amanner hereinafter described in detail.

The movable electric contact arm comprises a resilient strip ofconducting material having one the casing 25 has an arm 61 arrangedalong a portion of chamber 56 in front of the switch, and an electriccontact point 68 is secured to the inner face of the arm 61 adjacent itsend. The movable contact arm has a similar contact point 68 secured toits outer face adjacent its end which is connected to the overcenterspring 64 and in alignment with contact point 66. The movable contactarm 65 is biased to closed circuit position, that is, to normallymaintain the contact points 68 and 69 in engagement so that the relaywill not interrupt the circuit in which it is connected so long asnormal conditions exist in the circuit, but upon creation of abnormalconditions the thermostatic plate 45 will be deflected by the grid 46and move slide 54 which in turn moves lever 51 from the position of Fig.1 to the position shown in Fig. 4. This causes shifting movement of theovercenter spring 64 to move contact arm 65 and the contact point 66thereon away from contact point 68, breaking the circuit. If there isnothing, other than the abnormal current-conditions which heat the gridand cause deflection of the bimetallic plate which causes opening of thecircuit by operation of the switch as described, to prevent closingmovement of biased arm 65 the movable contact will automatically bereturned to closed circuit position when normal condition in the circuitagain prevails and permits cooling of the bimetallic element and returnto its original position, aashould be obvious. However, there areconditions under which it is desirable to maintain the switch andmovable electric contact arm from re-establishing or closing the circuitautomatically, and making it necessary to effect reclosing of thecircuit by hand operation, and the present invention provides means formaking the relay either automatically or hand resettable as desired,which feature will now be described.

The casing parts 26 and 21 have complemental faces which interfit .toform a housing for the stationary contact plates 35 and 36, movablecontact arm 65, and reset control plunger 10 and its associated parts.

The movable contact arm 65, a thin resilient strip of metal, previouslydescribed in part, has a curved substantially U-shaped portion 1|intermediate its ends arranged in alignment with the plunger 16, thesaid U-shaped portion 1i to accommodate and cooperate with the plungeras will be pointed out in detail hereinafter. The complemental faces ofthe casing parts 26 and 21 each have corresponding grooves 12 formedtherein adjacent their tops to form a chamber 13 when assembled. A coilspring 14 is mounted on the plunger stem 10 and partly compressedbetween a fixed collar 15 on the plunger stem and the. bottom of chamber13 to press against the collar and urge the plunger outwardly. A head 16is provided on the outer end of the plunger stem for engagement by afinger of the hand when turning the plunger to establish it in operativeand inoperative positions when making the relay either manually orautomatically resettable. A reset button 11 is conveniently provided onthe cover ill on the casing l0 adjacent the push button control station23. A spring plate 11* is rigidly connected at or near its bottom edgeto the inner face of the front cover Ill". The plate extends upward fromits points of attachment to the cover and its front face is in positionto be engaged by the rear end of the button 11 as clearly shown in Figs.2 and 3. The spring plate I'! has two arms, one of which designated asII is shown in Fig. l. The other arm is broken away but is similar as toshape and position except that it is left-handed instead of righthandedThe upper end of the arm ll is directly in front of the correspondinghead 16 at the right and the other arm is directly in front of thesimilar head at the left. When the plungers are in their forwardpositions to bring each head 16 into the position shown by dot-anddashlines in Fig. 3, the corresponding arms on the plate ll' are positionedto engage the heads to move the plungers inward or rearward. It will beapparent that with the plungers in their forward positions, they can bemoved simultane ously rearward by pressing on the button ll to flex thespring plate 11 rearward, the said spring plate through its respectivearms engaging and moving the respective plungers.

Each of the relay casing parts 25 and 2'! also has a groove 18 betweenthe chambers "l3 and 55 which afford, in conjunction with opening '18 atthe top of the casing, stabilized guided movement to the plunger 10, asbest shown in Figs. 8 and 9. Below the chamber 56 of the casing, and theU- shaped port-ion ll of the contact arm 65, the cas ing parts 26 and 21have grooves which provide a socket or chamber 80 in which the lower endof the plunger is located. Lugs 8| at the topof chamber 80 and at oneside thereof are situated to be engaged by the top edge or shoulasr of alug 82 radially projecting from the lower end of the plunger stem tohold the plunger in the inoperative position shown in Fig. 7, at whichtime the movable contact arm 65 is freely movable to open and closedcircuit positions relative to the fixed contact 68 in accordance withmovements of the bimetallic plate 45, as previously explained.

As shown best in Fig. 8, the bottom of U-shaped portion ll 01' themovable contact arm when in closed circuit position is in a planesubstantially parallel to but spaced from a plane in which the frontwall of socket B is located and along which the lug 82 of the plungermoves when the relay is used as manually resettable. lhe top edge orshoulder of lug 82 is in engagement withqthe confronting edge of thecontact arm when in closed position, as shown in Figs. and 8. At thistime the plunger spring is exerting force against the collar 15, whichis sufllcient to maintain the locking engagement between the movablecontact arm and shoulder of lug 82, as shown in Fig. 8, so long as theelectric circuit remains closed. As soon as the circuit is interrupted;however, the snap-action switch moves the movable contact arm back andclear of the shoulder of the lug 82, at which moment the spring Hexpands and forces the plunger up in the casing to the position of Fig.9, where the lug 82 sufficiently overlaps the bottom of U-shaped portionH to block circuit closing movement of the movable contact arm. Underthe then prevailing conditions, whether normal or abnormal in thecircult, closing of the circuit cannot be accomplished until the plungeris suiliciently depressed manually by pressure on its head 16 to movethe lug 8! beyond and clear of U-shaped portion ll of the movablecontact arm 55, to permit the arm 65 being moved by the thermal relayswitch mechanism to the position of Fig. 8. Obviously, when downwardpressure on the plunger is released the spring I4 urges it upward and itis arrested in its upward movement by engagement of the shoulder of lug82 against the confronting edge of the movable contact arm portion 1|.

Opening or rearward movement of the movable contact arm 85 is limited bystops or lugs 88 located in the chamber 58 of the casing 25 behind saidarm, and by similar lugs 84 in the chamber behind the switch lever 51for abutment thereby. Closing or forward movement of the same parts islimited by engagement of contact points 88 and 69.

It should be apparent from the foregoing that in order to make the relayautomatically resettable the plunger 70 is depressed as far as it canmove downwardly against spring I l and given a quarter turn to place thelug 82 in locked relation with the lugs 81 in chamber so that only thestem of the plunger extends across the U-shaped portion H of movablecontact arm 65 and spring 14 is inactive. The stem of plunger 10 is thendisposed across U-shaped portion ll but sufllcien'tly clear or spacedtherefrom to not interfere with operation of the contact arm 65 ineither direction of its circuit making and breaking movements. To makethe relay manually resettable the plunger is given a quarter turn inreverse direction to establish the lug 82 in operative relation "withthe movable contact arm 65 as previously explained. -The head 16 of theplunger is pointed at one end to conveniently serve as an indicator asto which of its selective positions, operative or inoperative, theplunger occupies, so that the operator will readily know whether therelay is manually or automatically resettable.

What I claim is:

l. A thermal relay for use in an electric circult and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, relatively movable electric contacts re spectively electricallyconnected to one of said terminals, a thermally responsive member, meansoperatively connecting said thermally responsive member to one of saidelectric contacts and said thermally responsive member normally servingupon the occurrence of variations in current in the circuit toautomatically actuate said connecting means and said one electriccontact to make and break said circuit, and control means movablymounted with respect to said base and having a portion free from saidmeans connecting said one contact and thermally responsive member andadapted to be selectively set in one position to permit automaticfunctioning of said thermally responsive member to relatively move theelectric contacts to make and break the circuit and to be set in anotherposition to engage said means connecting said one contact and thermallyresponsive member and prevent automatic engagement of said electriccontacts to make the circuit following a breaking of the same.

2. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, an arm movably mounted on the base, relatively movable electriccontacts respectively electrically connected to one of said terminals,one 01 said contacts being carried by said movable arm, a thermallyresponsive member operatively connected to said movable arm and normallyserving upon the occurrence of variations in current in the circuit toautomatically actuate said electric contact carried by said movable arm.

responsive member to actuate said movable arm and contact thereon tomake and break the circuit and to be set in another position to engagesaid movable arm to prevent automatic movement of the contact thereoninto circuit making position following a breaking of the same.

3. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, an arm movably mounted on the base, relatively movable electriccontacts respectively electrically connected to one of said terminals,one of said contacts being carried'by said movable arm, a thermallyresponsive member operatively connected to said movable arm and normallyserving upon the occurrence of variations in current in the circuit toautomatically actuate said electric contact carried by said movable armto make and break said circuit, and control means movably mounted withrespect to said base and comprising a member having a projection thereonadapted to be selectively set in one position to permit automaticfunctioning of said thermally responsive member to actuate said movablearm and contact thereon to make and break the circuit and to be set inanother position to permit said projection on said member to engage saidmovable arm to prevent automatic movement of the contact thereon intocircuit making position following a breaking of the same.

4. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, an arm movably mounted on the base, relatively movable electriccontacts respectively electrically connected to one of said terminals,one 01 said contacts being carried by said movable arm, a thermallyresponsive member operatively connected to said movable arm and normallyserving upon the occurrence of variations in current in the circuit toautomatically actuate said electric contact carried by said movable armto make and break said circuit, and control meansmovably mounted withrespect to said base and comprising a member having a projectionthereonadapted to be selectively set in one position to permit automaticfunctioning of said thermally responsive member to actuate said movablearm and contact thereon to make and break the circuit and to be set inanother position to permit said projection on said member to engage saidmovable armto prevent automatic movement of the contact thereon intocircuit making position following a breaking of the same, said controlmember also being movable to disconnect the projection thereon fromengagement with said arm and permit automatic movement of the contactthereon to circuit closing position following said disconnection.

5. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, an arm movably mounted on the base, relatively movable electriccontacts respectively electrically connected to one of said terminals,one of said contacts being carried by said movable arm, a thermallyresponsive member operatively connected to said movable arm and normallyserving upon the occurrence of variations in current in the circuit toautomatically actuate said electric contact carried by said movable armto make and break said circuit, a control member movably mounted withrespect to said base and having a projection thereon adapted to beselectively set in one position to permit automatic functioning of saidthermally responsive member to actuate said movable arm and contactthereon to make and break the circuit and to be set in another positionto permit said projection on said member to engage said movable arm toprevent automatic movement of the contact thereon into circuit makingposition following a breaking of the same, and a spring normallyengaging said control member and biasing the projection thereon in adirection to engage said movable arm following a breaking of thecircuit.

6. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, an arm movably mounted on the base,

relatively movable electric contacts respectively electrically connectedto one of said terminals, one of said contacts being carried by saidmovable arm, a thermally responsive member operatively connected to saidmovable arm and normally serving upon the occurrence of variations incurrent in the circuit to automatically actuate said electric contactcarried by said movable arm to make and break said circuit, a controlmember movably mounted with respect to said casing and having aprojection thereon adapted to be selectively set in one position topermit automatic functioning of said thermally responsive member toactuate said movable arm and contact thereon to make and brake thecircuit and to be set in another position to permit said projection onsaid member to engage said movable arm to prevent automatic movement ofthe contact thereon into circuit making position following a breaking orthe same, and a spring normally engaging said control member and biasingthe projection thereon in a direction to engage said movable armfollowing abreaking of the circuit, said control member being movableagainst the force of said spring to remove the projection fromengagement with said movable arm and permit automatic movement of thecontact thereon to circuit closing position following saiddisconnection.

7. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, a snap-acting toggle operatively mounted in said base andincluding a plurality of links and resilient means operatively connectedthereto, relatively movable electric contacts respectively electricallyconnected to one oi.said terminals, one of said electric contacts beinmounted on one of the component parts of and movable by said toggle, athermally responsive member operatively connected to one of thecomponent parts of said toggle and normally serving upon the occurrenceof variations in current in the circuit to automatically actuate saidtoggle to move the contact carried thereby to make and break saidcircuit, and control means movably mounted with respect to said base andadapted to be selectively set in one position to permit automaticfunctioning of said thermally responsive member to relatively move theelectric contacts to make and break the circuit and to be set in anotherposition to engage one component part of the toggle to prevent automaticengagement of said electric contacts to make the circuit following abreaking of the same.

8. A thermal relay ior use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, a snap-acting toggle operatively mounted on said base andincluding a plurality of links and resilient means operatively connectedthereto, one 01' said links being resilient, relatively movable electriccontacts respectively electrically connected to one of said terminals,one of said electric contacts being mounted on one of the componentparts of and movable by said toggle, a thermally responsive memberoperatively connected to one of the component parts of said toggle andnormally serving upon the occurrence of variations in current in thecircuitto automatically actuate said toggle to move the contact carriedthereby to make and break said circuit, and control means movablymounted with respect to said base and adapted to be selectively set inone position to permit automatic functioning of said thermallyresponsive member to relatively move the electric contacts to make andbreak the circuit and to be set in another position to engage onecomponent part of the toggle to prevent automatic engagement of saidelectric contacts to make the circuit following a breaking of the same.

9. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, a snap-acting toggle operatively mounted on said base andincluding a plurality of links and resilient means operatively connectedthereto, relatively movable electric contacts respectively electricallyconnected to one of said terminals, one of said electric contacts beingmounted on one of the component parts of and, movable by said toggle, athermally responsive member operatively connected to one of thecomponent parts of said toggle and normally serving upon the occurrenceof variations in current in the circuit to automatically actuate saidtoggle to move the contact carried thereby to make and break saidcircuit, and a control aember movably mounted with respect to said baseand having a projection thereon adapted to be selectively set in oneposition to permit automatic functioning of said thermally responsivemember to make and break the circuit and to be set in another positionto permit said proiection on said member to engage one component part ofthe toggle to prevent automatic engagei ment of said electric contactsto make the circult following a breaking of the same.

10. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, a snap-acting toggle operatively mounted on said base andincluding a plurality of resilient means operatively connected thereto,relatively movable electric contacts respectively electrically connectedto one of said terminals, one of said electric contacts being mounted onone of the component parts of and movable by said toggle, a thermallyresponsive member operatively connected to one of the component parts ofsaid toggle and normally serving upon the occurrence of variations incurrent in the circuit to automatically actuate said toggle to move thecontact carried thereby to make and break said circuit, a control membermovably mounted with respect to the base and having a projection thereonadapted to be selectively set in one position to permit automaticfunctioning of said thermally responsive member to make and break thecircuit and to be set in another position to permit said projection onsaid member to engage one component part of the toggle to preventautomatic engagement of said electric contacts to make the circuitfollowing a breaking of the same, and a spring normally engaging saidcontrol member and biasing the projection thereof in a direction toengage said one component part of the toggle following a breaking of thecircuit.

11. A thermal relay for use in an electric circuit and adapted to breakthe circuit upon the occurrence of abnormal current conditions in thecircuit, said relay comprising in combination, a base, terminal membersthereon by which the relay is adapted to be connected in an electriccircuit, a snap-acting toggle operatively mounted on said base andincluding a plurality of resilient means operatively connected thereto,relatively movable electric contacts respectively electrically connectedto one of said terminals, one of said electric contacts being mounted onone oi the component parts of and movable by said toggle, a thermallyresponsive member operatively connected to one of the component parts ofsaid toggle and normally serving upon the occurrence of variations incurrent in the circuit to automatically actuate said toggle to move thecontact carried thereby to make and break said circuit, a control membermovably mounted with respect to the base and having a projection thereonadapted to be selectively set in one position to permit automaticfunctioning of said thermally responsive member to make and break thecircuit and to be set in another position to permit said projection onsaid member to engage one component part of the toggle to preventautomatic engagement of said electric contacts to make the circuitfollowing a breaking of the same, and a spring normally engaging saidcontrol member and biasing the projection thereof in a direction toengage said one component part of the toggle following a breaking of thecircuit, said control member being movable against the force of saidspring to remove the projection from engagement with said one componentpart of the toggle and permit automatic engagement of said electriccontacts to make the circuit following said disconnection.

12. A thermal relay for use with electro-magnetic electric motorstarters comprising a body or housing of insulating material, said bodyincluding complemental parts forming a housing, an electrical resistanceunit housed in one part, electric terminals on said part by means ofwhich said resistance unit is adapted to be connected in an electriccircuit including the motor starter and devices controlled thereby, athermostatic element housed in said part and responsive to changes intemperatures occurring in the resistance unit, electric terminal memberson said one part by means of which said relay is adapted to be connectedin circuit with the electro-magnet of the motor starter, a movableelectric contact normally bridging and electrically connecting saidterminal members, a switch in said one part mechanically operable bymovement of said thermostatic element to move said movable contact outof co'htacting relation with one of said terminal members and interruptthe circuit, the second of said complemental parts of the body inter-,-;'-'=fitting with the first part to complete the housing at the sideof the body where the movable contact is located, and manually operablemeans located between said parts and selectively positionable to controlthe movable contact whereby the relay must be manually reset in oneposition of said means and is automatically reset in another position ofsaid means.

13. A thermal relay including a casing having two chambers therein, athermostatic element mounted in one of the chambers, an electricresistance unit adapted to be connected in a circuit, said electricresistance unit being mounted in said chamber to cause deflection of thethermostatic element due to variations in current conditions in saidcircuit, electric terminal members on the casing, a movable electriccontact member in the other chamber of the casing, a switch in saidother chamber operable to position said movable contact in closed andopen circuit positions relative to the terminal members, meansmechanically connecting the thermostatic element and switch to operatethe switch and effect movements of the movable contact member relativeto one terminal member to open and close said circuit in accordance withconditions aiiecting the thermostatic element, and means on the casingselectively positionable in operative and inoperative positions withrelation to the movable contact whereby the relay may operate asmanually or automatically resettable as desired.

14. A thermal relay including a casing having two chambers therein, athermostatic element mounted in one of the chambers, an electricresistance unit adapted to be connected in a circuit, said electricresistance unit being mounted in said chamber to cause deflection of thether- 4 mostatic element due to variations in current conditions in saidcircuit, electric terminal members on the casing, a movable electriccontact member in the other chamber of the casing, a switch in saidother chamber operable to position said movable contact in closed andopen circuit positions relative to the terminal members, a linkextending from one chamber into the other having guided reciprocatingmovement in the casing and mechanically connecting the thermostaticelement and switch to operate the switch and effect movements of themovable contact member relative to one terminal member to open mostaticelement due to variations in current conditions in said circuit,electric terminal members on the casing, a movable electric contactmember in the other chamber of the casing, a switch in said otherchamber operable to position said movable contact in closed and opencircuit positions relative to the terminal members, means mechanicallyconnecting the thermostatic element and switch to operate the switch andeffect movements of the movable contact member relative to one terminalmember to open and close said circuit in accordance with conditionsaffecting the thermostatic element, a manually operable spring pressedplunger in the casing adapted to automaticall block circuit closingmovement of the movable contact by said switch except upon manualoperation of the plungenand means to position said plunger in the casingrelative to the movable contact whereby the switch can be automaticallyoperable by th thermostatic element to close and open the circuit.

16. A thermal relay comprising a casing composed of inter-fitting partshaving opposed complemental portions forming a guideway, terminalmembers mounted on one of said parts and adapted to be connected in anelectric circuit, a movable electric contact electrically connected toone of said terminal members, a thermally responsive mechanism operablyconnected to said movable electric contact and serving upon theoccurrence of variations in current condition to actuate said movableelectric contact to make and break said electric circuit, and a manuallyoperable control member for the movable contact mounted between saidopposed complemental portions of said casing for guided movement withrespect to said movable electric contact.

17. A thermal relay comprising a casing composed of interfitting partshaving opposed complemental portion forming a, chamber and a guideway,terminal members mounted on one or said parts and adapted to beconnected in an electric circuit, a movable electric contactelectrically connected to one of said terminal members, a thermallyresponsive mechanism operably connected to said movable electric contactand serving upon the occurrence of variations in current conditions toactuate said movable electric contact to make and break said electriccircuit, a manually operable plunger mounted between said opposedcomplemental portions of said casing for guided movementwith respect tosaid movable electric contact, and a spring mounted in said housing andengaging said plunger to urge it in one direction.

18. A thermal relay comprising terminal members adapted to be connectedin an electric circuit, a movable electric contact electricall connectedto one of said terminal members, a thermally responsive mechanismoperably connected to said movable electric contact and serving upon theoccurrence of variations in current conditions to actuate said movableelectric contact to make and break said electric circuit, a manuallyoperable plunger having an engageable element Iorcontrolling the.movable contact, a spring coacting with said manually operable plungertonormally urge it in one direction} and a casing composed of lnterflttingparts and having opposed complemental portions forming a housing forsaid spring and a guideway for said manually operable plunger and alsohaving an engageable element with which said engaseable element on saidplunger is adapted to co-engage to hold said manually operable plungerin a selective predetermined position against the force of said spring.19. In combination with an encased thermal relay including terminals bywhich it may be connected in an electric circuit and also includingrelatively movable electric contacts and thermally responsive meansoperatively connected to one of said electric contacts to move the samerelatively to the other electric contact in response to variations incurrent in the circuit, a control member partially extending outward ofthe thermal rela case and selectively movable to a plurality ofpositions, means connected to said control member and operative in oneposition of said control member to render the thermally responsive meansautomatically operative upon the recurrence oi normal conditions in thecircuit to close said contacts and said means also being operative inanother position or said control member to prevent the closing or saidcontacts upon recurrence or normal conditions in the circuit until saidcontrol member i manual- 1y moved to a reset position, and means on saidoutward extending portion oi said control member to readily indicateexterior]? or said case in which position the means on said controlmember is disposed.

20. In combination with an encased thermal relay including terminals bywhich it may be connected in an electric circuit and also includingrelatively movable electric contacts and thermally responsive meansoperatively connected to one or said electric contacts to move the samerelatively to the other electric contact in response to variations incurrent in the circuit, an elongated control member partially extendingoutward of the thermal relay case and mounted for longitudinal movementand also being axially rotatable and selectively disposable in aplurality of positions, means connected to said control member andoperative in one position of said control member to render the thermallyresponsive means automatically operative upon the recurrence of normalconditions in the circuit to close said contacts and said means alsobeing operative in another position or said control member to preventthe closing of said contacts upon recurrence of normal conditions in thcircuit until said control member is manually moved longitudinallythereof to a reset position, a manually engageable member carried by theoutward extendin portion of said control member and by which it islongitudinally movable to said reset position and also axially rotatableto said plurality of positions, and indicating means carried by saidmanually engageable member to readily indicate exteriorly of said casein which position the means on said control member is disposed.

PAUL M. CHRISTENSEN.

